244 lines
7.0 KiB
Groff
244 lines
7.0 KiB
Groff
.TH UDEV 8 "October 2003" "" "Linux Administrator's Manual"
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.SH NAME
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udev \- Linux configurable dynamic device naming support
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.SH SYNOPSIS
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.BI udev " hotplug-subsystem"
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.SH "DESCRIPTION"
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.B udev
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creates or removes device node files usually located in the /dev directory.
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Its goal is to provide a dynamic device directory that contains only the files
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for devices that are actually present.
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.P
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As part of the
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.B hotplug
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subsystem,
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.B udev
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is executed if a kernel device is added or removed from the system.
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On device creation,
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.B udev
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reads the sysfs directory of the given device to collect device attributes
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like label, serial number or bus device number.
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These attributes are treated as a key
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to determine a unique name for device file creation.
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.B udev
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maintains a database for devices present on the system.
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.br
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On device removal,
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.B udev
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queries the internal database for the name of the device file to be deleted.
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.SH "CONFIGURATION"
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All
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.B udev
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configuration files consist of a set of lines of text. All empty
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lines, and lines beginning with a '#' will be ignored.
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.P
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.B udev
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expects its main configuration file at
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.I /etc/udev/udev.conf.
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The file consists of a set of variables and values that allow the user to
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override default udev values. The current set of variables that can be
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overridden in this file is:
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.TP
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.B udev_root
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This is the where in the filesystem to place the device nodes. The default
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value for this is
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.I /udev/
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.TP
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.B udev_db
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The name and location of the udev database. The default value for this is
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.I /udev/.udev.tdb
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.TP
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.B udev_rules
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This is the location of the udev rules file. The default value for this is
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.I /etc/udev/udev.rules
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.TP
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.B udev_permissions
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This is the location of the udev permission file. The default value for this is
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.I /etc/udev/udev.permissions
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.TP
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.B default_mode
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This is the default mode for all nodes that have no explicit match in the
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permissions file. The default value for this is
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.I 0666
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.br
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.P
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.RI "A sample " udev.conf " might look like this:
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.sp
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.nf
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# udev_root - where in the filesystem to place the device nodes
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udev_root="/udev/"
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# udev_db - The name and location of the udev database.
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udev_db="/udev/.udev.tdb"
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# udev_rules - The name and location of the udev rules file
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udev_rules="/etc/udev/udev.rules"
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# udev_permissions - The name and location of the udev permission file
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udev_permissions="/etc/udev/udev.permissions"
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# default_mode - set the default mode for all nodes that have no
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# explicit match in the permissions file
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default_mode="0666"
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.fi
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.P
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The rules for udev to use when naming devices may specified at
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.I /etc/udev/udev.rules
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or specified by the
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.I udev_rules
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value in the
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.I /etc/udev/udev.conf
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file.
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.P
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Every line in the rules file define the mapping between device attributes and
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the device file name. It starts with a keyword defining the method used to
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match, followed by one ore more keys to compare and the filename for the
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device. One ore more optional symlinks targeting the node may be specified.
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.br
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If no matching configuration is found, the default kernel device name
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is used.
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.P
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The line format is:
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.sp
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.I method, key,[key,...] name [, symlink]
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.sp
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where valid methods with corresponding keys are:
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.TP
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.B CALLOUT
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calling external program, that returns a string to match
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.br
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.RB "keys: " BUS ", " PROGRAM ", " ID
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.TP
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.B LABEL
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device label or serial number, like USB serial number, SCSI UUID or
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file system label
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.br
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.RB "keys: " BUS ", " SYSFS_
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.TP
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.B NUMBER
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device number on the bus, like PCI bus id
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.br
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.RB "keys: " BUS ", " ID
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.TP
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.B TOPOLOGY
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device position on bus, like physical port of USB device
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.br
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.RB "keys: " BUS ", " PLACE
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.TP
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.B REPLACE
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string replacement of the kernel device name
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.br
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.RB "key: " KERNEL
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.P
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The methods are applied in the following order:
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.BR CALLOUT ", " LABEL ", " NUMBER ", " TOPOLOGY ", " REPLACE "."
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.P
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.RB "The " NAME " ," SYMLINK " and " PROGRAM
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fields support simple printf-like string substitution:
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.TP
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.B %n
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The "kernel number" of the device.
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for example, 'sda3' has a "kernel number" of '3'
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.TP
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.B %M
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The kernel major number for the device.
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.TP
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.B %m
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The kernel minor number for the device.
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.TP
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.B %b
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The bus id for the device.
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.TP
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.B %c
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The CALLOUT program returned string.
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(This does not work within the PROGRAM field for the obvious reason.)
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.TP
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.B %D
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Use the devfs style disk name for this device.
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For partitions, this will result in 'part%n'
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If this is not a partition, it will result in 'disc'.
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.P
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.RI "A sample " udev.rules " might look like this:"
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.sp
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.nf
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# if /sbin/scsi_id returns "OEM 0815" device will be called disk1
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CALLOUT, BUS="scsi", PROGRAM="/sbin/scsi_id", ID="OEM 0815", NAME="disk1"
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# USB printer to be called lp_color
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LABEL, BUS="usb", SYSFS_serial="W09090207101241330", NAME="lp_color"
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# sound card with PCI bus id 00:0b.0 to be called dsp
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NUMBER, BUS="pci", ID="00:0b.0", NAME="dsp"
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# USB mouse at third port of the second hub to be called mouse1
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TOPOLOGY, BUS="usb", PLACE="2.3", NAME="mouse1"
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# ttyUSB1 should always be called pda with two additional symlinks
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REPLACE, KERNEL="ttyUSB1", NAME="pda", SYMLINK="palmtop handheld"
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# multiple USB webcams with symlinks to be called webcam0, webcam1, ...
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LABEL, BUS="usb", SYSFS_model="WebCam V3", NAME="video%n", SYMLINK="webcam%n"
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.fi
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.P
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Permissions and ownership for the created device files may specified at
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.I /etc/udev/udev.permissions
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or specified by the
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.I udev_permission
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value in the
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.I /etc/udev/udev.conf
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file.
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.br
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Every line lists a device name followed by owner, group and permission
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mode. All values are separated by colons. The name field may contain a
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pattern to apply the values to a whole class of devices.
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.br
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If
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.B udev
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was built using klibc or is used before the user database is accessible (e.g.
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.BR initrd "(4)), only numeric owner and group values may be used."
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.sp
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.RI "A sample " udev.permissions " might look like this:"
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.sp
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.nf
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#name:user:group:mode
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input/*:root:root:644
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ttyUSB1:0:8:0660
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video*:root:video:0660
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dsp1:::0666
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.fi
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.P
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A number of different fields in the above configuration files support a simple
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form of shell style pattern matching. It supports the following pattern characters:
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.TP
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.B *
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Matches zero, one, or more characters.
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.TP
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.B ?
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Matches any single character, but does not match zero characters.
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.TP
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.B [ ]
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Matches any single character specified within the brackets. For example, the
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pattern string "tty[SR]" would match either "ttyS" or "ttyR". Ranges are also
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supported within this match with the '-' character. For example, to match on
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the range of all digits, the pattern [0-9] would be used. If the first character
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following the '[' is a '!' then any character not enclosed is matched.
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.SH "FILES"
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.nf
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/sbin/udev udev program
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/etc/udev/* udev config files
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/etc/hotplug.d/default/udev.hotplug hotplug symlink to udev program
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.fi
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.LP
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.SH "SEE ALSO"
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.BR hotplug (8)
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.PP
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The
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.I http://linux-hotplug.sourceforge.net/
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web site.
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.SH AUTHORS
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.B udev
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was developed by Greg Kroah-Hartman <greg@kroah.com> with much help from
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Dan Stekloff <dsteklof@us.ibm.com>, Kay Sievers <kay.sievers@vrfy.org>, and
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many others.
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